Ask HN: How do you show off your portfolio of dead side projects?

Well, Depending on what kind of projects these are, keeping a copy of the website somewhere is usually a good start.

If it is program based, keeping screenshots or recording of what the software did can also be of help.

My third and final tip would be to write some form of post explaining what the project was and maybe why you think it didn't take off.

Buy 1 cheap domain for 10 years or get a free domain (.gs), buy 1 cheap hosting for 10 years or use some free hosting (Red Hat Openshift) and deploy all your stuff there + make sure you have README.md in all your projects with single-script deploy script. As EKSolutions said: screenshots, documentation etc.

Well an alternative is to have an online portfolio site where you can keep screenshots, examples or even gifs showing your the features of these sites. Also, you should keep the code in case you want to show it as well